Hydrogen Sulphide

Hydrogen Sulphide is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is partially responsible for the foul odor of rotten eggs and flatulence.
It often results from the bacterial break down of sulfites in nonorganic matter in the absence of oxygen, such as in swamps and sewers (anaerobic digestion). It also occurs in volcanic gases, natural gas and some well waters. The odor of H2S is commonly misattributed to elemental sulfur, which is in fact odorless.
Hydrogen sulfide is considered a broad-spectrum poison, meaning that it can poison several different systems in the body, although the nervous system is most affected.
For detection of hydrogen sulfide (or Hydrogen Sulphide), a portable or fixed gas detector can be used. Most portable H2S detectors are suitable for work in hazardous areas. We also offer a wide variety of fixed H2S detectors. Contact Airmet for more options.
Hydrogen Sulphide Characteristics
Synonyms Sulphuretted hydrogen, rotten egg gas, sewer gas, stink damp
CAS No. 6/4/7783
Chemical formula H2S
Vapour density 1.19 (air = 1)
Safe Work Australia ES TWA 10 ppm
STEL 15 ppm
Flammable limits LEL 4.0 % by volume
UEL 45.5 % by volume
Equipment group IIB
Temperature classification T3
Chemical/physical properties Hydrogen sulphide at room temperature is a colourless, flammable gas with a pungent “rotten egg” odour.  Although easily detectable by smell at low concentrations (usually below about 0.1 ppm), prolonged exposure to non-lethal concentrations (150 – 200 ppm) can lead to olfactory fatigue whereby higher and potentially lethal concentrations cannot be perceived.
Hazardous properties At low concentrations, hydrogen sulphide is an irritant to the eyes and respiratory tract. At higher concentrations it inhibits critical respiratory enzymes, leading to paralysis of the respiratory centre and rapid death by asphyxiation; this can occur at concentrations as low as 1,000 to 2,000 ppm.
Uses and occurrence Hydrogen sulphide is produced naturally when organic matter decays under anaerobic (no oxygen) conditions. It is a by-product of petroleum refining and is used in the production and processing of synthetic rubbers, fabrics (e.g. rayon), dyes, leather and even sugar. It is found in sewer gas and in certain coal seams (sometimes in a mixture with methane) called “stink damp”.
Detectors available Electrochemical (0 – 500 ppm)
Gas detector tube (0.2 ppm – 40 % by volume)
Colorimetric paper tape (0 – 20 ppm and 0 – 90 ppb)
Suggested alarm levels Lo: 10 ppm
Hi: 15 ppm


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